Effect of hyperthyroidism on spontaneous physical activity and energy expenditure in rats

James A. Levine, Jonas Nygren, Kevin R. Short, K. Sreekumaran Nair

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Abstract

Thyroid hormone excess is associated with increased energy expenditure. The contributions of increases in spontaneous physical activity and nonexercise activity thermogenesis (NEAT) to this effect have not been defined. To address the hypothesis that hyperthyroidism is associated with increased spontaneous physical activity and NEAT, we rendered rats hyperthyroid by using continuous infusion of high-dose triiodothyronine for 14 days and measured the effects on physical activity and NEAT. On day 14, in the hyperthyroid group the mean ± SD triiodothyronine concentration was 755 ± 137 (range 574-919) ng/dl and in the control group 59 = 0.5 (58-59) ng/dl. Over the 14-day treatment period, mean spontaneous physical activity increased in the hyperthyroid rats from 24 ± 7 to 36 ± 6 activity units (AU)/min; P < 0.001 but did not increase in the controls (23 ± 7 vs. 22 ± 4 AU/min). Also, over the 14-day period, daily NEAT increased in the hyperthyroid rats from 8.1 ± 2.8 to 19.7 ± 5.0 kcal/day (P < 0.001) but did not increase in the controls (8.7 ± 3.5 cf 9.4 ± 1.7 kcal/day; not significant). In conclusion, hyperthyroidism is associated with increased spontaneous physical activity and NEAT.

Original languageEnglish (US)
Pages (from-to)165-170
Number of pages6
JournalJournal of Applied Physiology
Volume94
Issue number1
DOIs
StatePublished - Jan 1 2003

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Keywords

  • Thyroid hormone

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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